Science 3200 Unit 1 Part 2

Bonding Bonding of elements is the attraction between atoms or ions Bonds that are formed between two non-metals (i.e. elements found to the right of the ladder on the periodic table) result in molecular compounds Bonds that are formed between a metal and a non-metal (i.e. one from the left and one from the right of the ladder) result in ionic compounds

Bonding Ex. State whether each compound is molecular or ionic. NaCl CF4 LiBr

Bonding Some atoms will combine with other atoms of the same element. These atoms are found in nature like this. These are: Hydrogen (H2) - Bromine (Br2) Nitrogen (N2) - Iodine (I2) Oxygen (O2) - Astatine (At2) Fluorine (F2) - Phosphorus (P4) Chlorine (Cl2) - Sulfur (S8)

Bonding Covalent Bonding (Molecular Compounds) Sharing of electrons the two non-metals both want to gain electrons (to be like the noble gases), since both cannot gain electrons at the same time they share. The unit formed by a covalent bond is called a molecule (it is neutral; it has no charge)

Bonding Ionic Bonding Gaining and losing electrons to form stable compound The unit formed by an ionic compound is a formula unit These form neutral compounds by the number of electrons lost is equal to the number taken up

Compounds Molecular Compounds Involve the sharing of electrons resulting in covalent bonding Composed of two non-metals Exist as individual molecules May or may not be in lowest whole number ratios

Naming Molecular Compounds Mono-atomic elements Mono means one, so these are elements that exist on their own in nature. Namely the noble gases: He – helium Ne – neon Ar – argon Kr – krypton Xe – xenon Rn – radon No need to memorize these as they are listed in the periodic table

Naming Molecular Compounds Diatomic molecular compounds These are non-metals that exist in nature as two atoms joined together. They are: H2 – hydrogen O2 – oxygen N2 – nitrogen Cl2 – chlorine F2 – flourine Br2 – bromine I2 - iodine

Naming Molecular Compounds Polyatomic molecular elements These are non-metals that exist in nature with many atoms joined together These are: S8 – sulfur O3 – ozone P4 – phosphorus (red)

Naming Molecular Compounds Trivial names These are names on compounds that do not follow the guidelines put out by IUPAC. These are: H2O – water H2O2 – hydrogen peroxide NH3 – ammonia C12H22O11 – sucrose CH4 – methane CH3OH – methanol C2H5OH - ethanol

Naming Molecular Compounds For binary molecular compounds, we use prefixes to indicate the number of atoms that are present in the compound. These are: Mono – one Di – two Tri – three Tetra – four Penta – five Hexa – six Hepta – seven Octa – eight Nona – nine Deca - ten

Naming Molecular Compounds When writing the name of a molecular compound start with the first element, not changing the name, except for adding the prefix. Then write the name of the second element with the prefix and changing the ending of the name to –ide. Note: the prefix mono on the first element only is optional.

Naming Molecular Compounds For example, name the compound CCl4 The first element is carbon and there is only one of them. The second element is chlorine and there are 4 of them. Therefore the name would be monocarbon tetrachloride or carbon tetrachloride

Naming Molecular Compounds Ex 2. Write the name for P4F6. Sol’n: The first element is phosphorus and there are four atoms. The second element is fluorine and there are six atoms. Therefore the name of this compound is: tetraphosphorus hexafluoride

Naming Molecular Compounds Your turn. Name each of the following. P4F5 C2O4 NO3 Cl2O N3Br2 O6I2

Writing Molecular Formulas When writing molecular formulas you look up each element on the periodic table to determine the chemical symbol for the element. (Don’t forget that the ending on the second element has been changed to –ide) Use the prefix on each element to determine the number of atoms present. Write this number to the right of the symbol and as a subscript.

Writing Molecular Formulas Ex. Write the formula for diboron hexahydride. The first element is boron which is B and di means 2. The second element is hydride (or hydrogen) which is H and hexa means 6.  We have B2H6

Writing Molecular Formulas Ex. Write the formula for nitrogen triiodide. The first element is nitrogen which is N and since there is no prefix there is only one. The second element is iodide (or iodine) and tri means 3.  We have N1I3 or NI3.

Writing Molecular Formulas Your turn. Write the formulas for each of the following. Carbon disulfide Dinitrogen pentabromide Silicon trifluoride Hexaphosphorus pentachloride

Ionic Compounds Ionic Compounds: Involve the transfer of electron(s), i.e gaining and losing electrons, resulting in ionic bonding Made up of two oppositely charged ions (metal and non-metal, or combination involving a polyatomic ion) Are always written as empirical formulas (lowest whole number ratio)

Naming Ionic Compounds There are two categories of ionic compounds that we will deal with. 1. Binary ionic Simple ions (only single charges) 2. Polyatomic ions (complex ions)

Naming Ionic Compounds Binary ionic compounds are composed of a metal ion (+) and non-metal ion (-). Binary simply means that only 2 ions are involved. Ex. NaCl – the combination of a sodium ion and a chloride ion.

Naming Ionic Compounds Rules for naming simple binary ionic compounds (meaning a compound with only two elements): Name the metal (+) by writing the full name of the metal. Name the non-metal (-) by shortening the name of the atom and adding the –ide ending.

Naming Ionic Compounds Ex. NaCl  sodium chloride CaF2  calcium fluoride K2O  potassium oxide **Note: Do NOT use prefixes – they are for molecular compounds only (i.e. two non-metals)

Naming Ionic Compounds Your turn. Name the following: LiBr AlCl3 Rb2S Mg3P2 CaO

Writing Ionic Formulas Rules for writing binary ionic formulas: Write down the symbols of the ions involved. Cross over the charges and write as subscripts. Determine the lowest whole number ratio of ions that will give a net charge of zero. You do not need to write 1’s.

Writing Ionic Formulas Ex. 1) Write the chemical formula for potassium bromide. 2) Write the chemical formula for calcium oxide. 3) Write the chemical formula for magnesium iodide.

Writing Ionic Formulas Your turn. Write the chemical formula for each compound: Sodium sulfide Aluminum bromide Barium iodide Magnesium nitride Aluminum nitride

Naming Compounds with Polyatomic Ions A polyatomic ion is two or more atoms covalently bonded together that carry an overall charge. Since they have a charge they can gain or lose electrons to form ionic compounds. These ions are listed on your sheet but this list is not exhausted, i.e. There are more polyatomic ions than what’s listed.

Naming Compounds with Polyatomic Ions To identify these compounds look at the elements involve. If you have more than two elements in the compound and the compound is not in your trivial names list than it contains a polyatomic ion. You name these the same way you name ionic compounds: look up the element/polyatomic ion and write the names down changing the second name to have the ending –ide.

Naming Compounds with Polyatomic Ions Ex 1. (NH4)3PO4 Ex 2. Cr(NO3)3

Naming Compounds with Polyatomic Ions Your turn. Write the name of the following compounds. Zn(OH)2 Pb(NO3)2 Mg(CH3COO)2 Na3BO3 K2Cr2O7

Writing Compounds with Polyatomic Ions When writing the formulas for compounds containing a polyatomic ion(s), you treat the ion as a single unit, not as individual elements. If you need to write a subscript for a polyatomic ion, then you must enclose the ion in brackets. Remember to use the charges on the polyatomic ions to determine how many you need to have a balanced compound, NOT the subscripts!!!

Writing Compounds with Polyatomic Ions Ex 1. sodium chlorite Ex 2. iron (III) sulfate Ex 3. ammonium permanganate

Writing Compounds with Polyatomic Ions Your turn. Write the formula for each of the following. Sodium hydroxide Potassium bicarbonate Potassium carbonate Magnesium hydroxide Ammonium sulfate